Wireless charging for Electric Vehicles (EV)

The charging technology for electric vehicles (EVs) is one of the key enablers to facilitate wider adoption of EV in the present scenario. There are many ways of charging the EV such as; Conductive charging (via coupler and cable), Inductive charging (wireless charging), Battery switching (rapidly switching the battery) and Fuel cell (refilling of hydrogen).

A technology called WiTricity for wirelessly energy transmission over a fair distance as reported by Massachusetts Institute of Technology (MIT) in July 2007 provided a way to supply energy for several devices especially for electric vehicles. It is the transmission of electrical energy from a power source to an electrical load without physical conductors with the use of resonant inductive coupling.

Wireless Power Transfer or Inductive Power Transfer (IPT) is similar but not same as traditional magnetic induction, such as is used in power transformers, where conductive coils transmit power to each other wirelessly, over very short distances. It works on the principle of mutual induction between the transmitter and receiver coils. It has the advantage of enhancing the aesthetics of products and making it adaptable to all environments while being able to charge several devices with a single transmitter.

This technology is new and hence the major drawback it faces is low efficiency which I think with enhanced research and investment; the efficiency and acceptability would be increased in future.

Above image describes the principle of Wireless charging power source, on the left, is connected to AC power. The blue lines represent the near field induced by the power source. The yellow lines represent the flow of energy from the source to the Wireless charging capture coil, which is shown powering a light bulb. It shows how the magnetic field can wrap around a conductive obstacle between the power source and the capture device.

The versatility of charging a product wirelessly ensures that it can be used for a wide variety of applications. The main advantage of using wired charging is that it is inexpensive. However, with the new technologies being developed, wireless charging will soon replace these traditional methods as an inexpensive and practical alternate method to recharge devices.

In wireless power transfer, the power sources and portable devices are specially designed using magnetic resonators that efficiently transfer power over large distances via the magnetic near-field. Another major problem of cable charging is the wear and tear of sockets due to frequent use; this is eliminated in the wireless charging as no wires or connectors are required.

The power transfer becomes efficient if we use resonant inductive coupling. Resonant inductive coupling is the near field wireless transmission of electrical energy between two coils that are tuned to resonate at the same frequency. Inductive Power Transfer (IPT) wireless charging uses strongly coupled magnetic resonance to transfer power from a transmitting pad on the ground to a receiving pad on an electric car as shown in the image.

To charge, an electric car simply has to be parked or even driven over a pad. It has lower risk of electrical shock since no exposed contacts as compared with conductive charging. It also enables the dynamic charging while EVs are on the move.

The main advantages of wireless charging, the power can be delivered in any direction i.e. omnidirectional. The magnetic fields used in the wireless transfer of power are not harmful to living beings. Aesthetically is better option due to de cluttering of office or living space. No need for meter rooms and electrical closets.

Reduction of e-waste by eliminating the need for power cords; hence, it directly contributes in improving environment. It also gives a protected connection for all equipments and eliminates corrosion and direct contact of water or oxygen in the atmosphere. It makes way for automatic wireless charging for future hybrid and all electric passenger and commercial vehicles, at home, in parking garages, at fleet depots, and at remote kiosks.

The demerits include power transfer only takes place if the flux satisfies certain conditions. It becomes inefficient as the distance between the transmitter and receiver increases. There could be a loss of power transmission if there is a strong ferromagnetic substance present between the transmitter and receiver.

To make Wireless charging on a large scale in future could be possible if the efficiency of the power transmitted increases. It should reduce the power loss when the distance between the charging pad and the devices increases. The system must be made more cost effective to make it a viable alternate solution to wired charging.  


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